JP2010145564A - Liquid crystal device and electronic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electronic apparatus that can display an image with a wide viewing angle by improving viewing angle characteristics without constituting a zigzag form for multi-domain formation. <P>SOLUTION: In a method for driving a liquid crystal device which includes a pair of substrates facing each other and liquid crystal held between the pair of substrates and is driven so that a longer-axis direction of liquid crystal molecules of the liquid crystal initially aligned approximately in a normal direction to the pair of substrates approximates a direction along the pair of substrates, and is provided with pixels for displaying an image, the liquid crystal molecules are driven so as to form a first display state and a second display state between which viewing angle characteristics of an image displayed by the pixels are in a complementary relation to each other. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a liquid crystal device and an electronic apparatus.

  In a liquid crystal device that drives a liquid crystal to control brightness for each pixel and displays an image, a VA (Vertical Alignment) method is often used as one of driving methods in which the response speed of the liquid crystal is fast. The VA mode includes a pair of opposing substrates and a liquid crystal layer sandwiched between the pair of substrates, and the length of liquid crystal molecules initially aligned in a substantially normal direction (longitudinal direction) with respect to the pair of substrates. This is a so-called vertical electric field type driving method in which an axial direction is driven so as to approach a direction along a pair of substrates for each pixel by a voltage applied to the liquid crystal layer.

  By the way, such a VA liquid crystal device has a viewing angle characteristic of other driving methods, for example, a horizontal electric field in which the major axis direction of liquid crystal molecules is rotated in a direction along the substrate surface by a voltage applied to the liquid crystal layer. There is a problem that it is inferior to the method. Therefore, conventionally, a method for improving viewing angle characteristics in a VA liquid crystal device has been proposed. For example, Patent Document 1 discloses a method in which a plurality of initial alignment directions of a liquid crystal layer are formed into a multi-domain so that there are a plurality of major axis directions of liquid crystal molecules exhibited when a voltage is applied to the liquid crystal layer. Has been. By doing so, the alignment direction in the pixel is divided and formed, so that a wide viewing angle can be obtained.

JP-A-11-258606

  However, in the technique disclosed in Patent Document 1, zigzag protrusions or depressions or slits must be arranged in parallel at a predetermined pitch in order to form a multi-domain, and a complicated structure is provided in a liquid crystal device. There was a need. For this reason, it has been difficult to physically form such a zigzag structure in a liquid crystal device having a small pixel pitch in order to display a high-definition image. Therefore, there has been a demand for a technique for improving the viewing angle characteristics and displaying an image having a wide viewing angle without configuring such a zigzag shape.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

  Application Example 1 It includes a pair of opposing substrates, a liquid crystal layer sandwiched between the pair of substrates and initially oriented in a substantially normal direction with respect to the pair of substrates, and a pixel for displaying an image. A liquid crystal device, wherein a first display state and a second display state in which viewing angle characteristics of images displayed by the pixels are complementary to each other are combined and displayed.

  According to this configuration, since two display states having complementary viewing angle characteristics are combined and displayed for the image displayed on the pixel, an image display having a wide viewing angle is performed according to the two display states. be able to.

  Application Example 2 In the liquid crystal device, the voltage value applied to the liquid crystal layer in the first display state and the voltage value applied to the liquid crystal layer in the second display state. And are different from each other.

  According to this configuration, the voltage value of the voltage applied to the liquid crystal layer is different, thereby forming a display state in which the viewing angle characteristics of the image are complementary to each other. Therefore, by changing the applied voltage, a wide viewing angle can be obtained. Image display can be performed.

  Application Example 3 In the above-described liquid crystal device, the voltage value of the voltage applied to the liquid crystal layer in the first display state is the voltage value of the voltage that maximizes the brightness of the image displayed by the pixel. A voltage value applied to the liquid crystal layer in the second display state is lower than a voltage value at which the brightness of the image displayed by the pixel is maximized. It is set to a range.

  According to this configuration, an image having viewing angle characteristics complementary to each other is displayed by a voltage applied to the liquid crystal layer that is higher and lower than a voltage applied when the image is brightest. Therefore, for example, by using two display states having substantially the same brightness and complementary viewing angle characteristics, it is possible to easily display an image with a wide viewing angle without changing the brightness of the image.

  Application Example 4 In the liquid crystal device, the liquid crystal device includes a period driven in the first display state and a period driven in the second display state within the image display period. Features.

  According to this configuration, since images having complementary viewing angle characteristics are displayed within the image display period, images having complementary viewing angle characteristics are temporally integrated and synthesized. As a result, image display with a wide viewing angle can be performed.

  Application Example 5 In the liquid crystal device, the period driven in the first display state and the period driven in the second display state are periods having the same time length. To do.

  According to this configuration, two display states having complementary viewing angle characteristics are formed for the same time within the image display period. Therefore, an image synthesized by temporal integration has a wide viewing angle. The probability of becoming an image increases.

  Application Example 6 In the liquid crystal device, the pixel includes a plurality of sub-pixels, and the plurality of sub-pixels include the sub-pixel driven in the first display state and the second sub-pixel. And the sub-pixel driven in a display state.

  According to this configuration, since images having complementary viewing angle characteristics are simultaneously displayed during the image display period, images having complementary viewing angle characteristics are spatially integrated and synthesized. As a result, image display with a wide viewing angle can be performed.

  Application Example 7 In the liquid crystal device, the sub-pixel driven in the first display state and the sub-pixel driven in the second display state have a pixel area size. It is characterized by being equal.

  According to this configuration, images having complementary viewing angle characteristics are simultaneously displayed with the same size in the image display period, so that an image that is spatially integrated and synthesized is an image with a wide viewing angle. The probability of becoming higher.

  Application Example 8 In the liquid crystal device, light having a wavelength of any color of R (red), G (green), and B (blue) is emitted from the pixel.

  According to this configuration, it is possible to synthesize the viewing angle of the display image for any of the colors R, G, and B with images having viewing angle characteristics that are complementary to each other. As a result, color images can be displayed with a wide viewing angle.

  Application Example 9 In the liquid crystal device, a retardation plate whose refractive index in the thickness direction is smaller than the refractive index in the in-plane direction with respect to the pixels is disposed outside the pair of substrates. It is characterized by.

  According to this configuration, since the refractive index anisotropy exhibited by the liquid crystal molecules can be compensated by the retardation plate, it can be expected to realize a liquid crystal device capable of displaying an image with a wider viewing angle.

  Application Example 10 In the liquid crystal device, the pixel is a pixel that reflects light incident on the pixel and displays the image.

  According to this configuration, it is possible to realize a reflective liquid crystal device capable of displaying an image with a wide viewing angle by displaying images having viewing angle characteristics complementary to each other.

  Application Example 11 Electronic equipment including the liquid crystal device.

  According to this device configuration, it is possible to provide an electronic device capable of displaying an image with a wide viewing angle by displaying images having viewing angle characteristics complementary to each other.

  Hereinafter, the present invention will be described based on examples. It should be noted that the drawings used in the following description may be exaggerated for the sake of description, and needless to say, they do not necessarily indicate the actual size or length.

  FIG. 1 is a perspective view schematically showing a schematic configuration of an electronic viewfinder 1 as an electronic apparatus including a liquid crystal device 100 according to an embodiment of the present invention. The electronic viewfinder 1 is a reflective display device, and includes a liquid crystal device 100 serving as a display device that displays an image by pixels formed in a planar area, and an image (color) output from a video device such as a video camera. Image).

  More specifically, light from a light source such as an LED (organic light emitting diode or inorganic light emitting diode) irradiates the polarizing beam splitter 5. In this embodiment, the polarization beam splitter 5 is configured to reflect S-polarized light and pass P-polarized light, and out of light from the light source, S-polarized light (light that vibrates in the X-axis direction as shown). Is reflected. The reflected S-polarized light is incident on the display surface of the liquid crystal device 100 from a substantially normal direction (this is the Z-axis direction as shown). Here, in the liquid crystal device 100, the direction inclined 45 degrees counterclockwise to the Y-axis direction orthogonal to the X-axis in the display surface as shown in the drawing is the slow phase with the X-axis direction as the reference (0 degree). The alignment direction of the liquid crystal layer is formed so as to be an axis (described later), and is configured to function as a retardation plate. Then, the S-polarized light incident on the liquid crystal device 100 is reflected and emitted toward the polarization beam splitter 5 again. At this time, the incident S-polarized light is optically modulated and given a phase difference of ½ wavelength, and the polarization axis is rotated 90 degrees to become P-polarized light (light that vibrates in the Y-axis direction as shown). . In the polarization beam splitter 5, since the polarization axis is formed in the same direction as the P polarization, the P polarization emitted from the liquid crystal device 100 passes through the polarization beam splitter 5. The passed P-polarized light is then emitted through an optical system 3 such as an eyepiece (not shown). An observer of the electronic viewfinder 1 visually recognizes an image displayed by each pixel of the liquid crystal device 100 by looking at the emitted P-polarized light.

  The liquid crystal device 100 according to the present embodiment includes a liquid crystal device having a structure in which a substrate 10 and a substrate 20 as a pair of substrates are bonded with a sealing material (not shown) with a liquid crystal layer (not shown) sandwiched between them. The panel 30 and the phase difference plate 50 are included. In this embodiment, the liquid crystal panel 30 is a VA mode reflective panel, and the retardation plate 50 is a C plate. As is well known, in the VA mode, in the initial alignment state, the major axis direction of the liquid crystal molecules is the normal direction of the substrate 10 (or the substrate 20), that is, the direction along the Z-axis direction. The refractive index in the Z-axis direction is large. Therefore, the phase difference when viewed from an oblique direction with respect to the Z-axis direction is compensated by a C plate having a refractive index nz in the Z-axis direction smaller than the refractive index nx in the X-axis direction and the refractive index ny in the Y-axis direction. I can do it. Although the retardation plate 50 is illustrated as being separated from the liquid crystal panel 30, it may be attached to the liquid crystal panel 30.

  Next, the liquid crystal panel 30 will be described with reference to FIGS. FIG. 2 is an explanatory diagram of the substrate 10 constituting the liquid crystal panel 30, and FIG. 3 is an explanatory diagram illustrating the entire configuration of the liquid crystal panel 30.

  First, the substrate 10 will be described with reference to FIG. As shown in the drawing, a substrate 10 is formed by forming a scanning drive circuit 11 and a data drive circuit 12 on a flat plate (the drawing surface side) of glass, quartz, resin, ceramic, or the like on the outer periphery thereof. Further, the scanning line 111 is wired from the scanning driving circuit 11 and the data line 121 is wired from the data driving circuit 12 as shown in FIG. The thin film transistor 14 is supplied to the thin film transistor 14 formed near the intersection of the scanning line 111 and the data line 121 corresponding to each pixel, and the on / off state of the thin film transistor 14 is controlled by the voltage supplied by the scanning line 111. Is done. Further, when the thin film transistor 14 is turned on, the voltage supplied by the data line 121 is electrically applied to the electrode provided for each pixel.

  When the substrate 10 and the substrate 20 (not shown) are bonded to each other, an electrode (hereinafter referred to as “pixel electrode”) provided on the substrate 10 side in each pixel and the substrate 20 as indicated by a two-dot chain line in the figure. The electrodes (hereinafter referred to as “common electrodes”) that are provided on the side and supply a common potential (for example, ground potential) to all the pixels are configured to face each other across the liquid crystal layer. Therefore, in each pixel, when the thin film transistor 14 is turned on, a differential voltage between the voltage supplied by the data line 121 and the common electrode voltage is applied to the liquid crystal layer corresponding to each pixel, and light modulation corresponding to the differential voltage is performed. And the brightness of the pixel is controlled.

  In this embodiment, the pixel electrode is a reflective electrode configured to reflect light. Further, in this embodiment, for simplification of explanation, it is assumed that six pixel electrodes are arranged in the X-axis direction and three pixel electrodes are arranged in the Y-axis direction, and the corresponding pixels are similarly formed. . Of course, in practice, hundreds to thousands of pixels are usually formed in each of the X-axis direction and the Y-axis direction.

  Next, the configuration of the liquid crystal panel 30 will be described with reference to FIG. FIG. 3A is a plan view of three pixels arranged in the X-axis direction as viewed from the substrate 20 side. FIG. 3B is a partial cross-sectional view of the configuration, showing a CC cross section in FIG. FIG. 3C is a schematic diagram showing the alignment state of the liquid crystal molecules in the liquid crystal layer. As shown in FIG. 3B, the liquid crystal panel 30 has a structure in which the liquid crystal layer 40 is sandwiched between the substrate 10 and the substrate 20.

  As shown in FIGS. 3A and 3B, the substrate 20 has a region corresponding to a pixel that performs light modulation as a light incident region, and the thin film transistor 14 and other regions serve as light shielding regions. As described above, the predetermined light-shielding layer BM made of a metal film or the like is formed on the light-transmitting flat plate B such as glass, quartz, or resin. In this embodiment, an R filter layer, a G filter layer, and a B filter layer that transmit light having wavelengths of R (red), G (green), and B (blue) are formed in the light incident region, respectively. ing.

  A common electrode made of a translucent material (for example, ITO) is formed on the flat plate B and the light shielding layer BM on the liquid crystal layer 40 side. Further, an alignment film B is formed on the common electrode on the liquid crystal layer 40 side so as to cover the common electrode. The alignment film B is made of a composition based on polyimide, for example.

  As described above, the substrate 10 is a flat plate made of glass, quartz, resin, ceramic, or the like, and the pixel electrode is formed on the surface on the liquid crystal layer 40 side corresponding to the pixel region. Since the pixel electrode is also a reflective electrode, materials such as aluminum, aluminum and copper, an alloy of aluminum and neodymium, and APC (silver-palladium-copper alloy) are used. Further, an alignment film A is formed on the liquid crystal layer 40 side of the pixel electrode so as to cover the pixel electrode. The alignment film A is made of, for example, a composition based on polyimide. Although not shown, scanning lines 111, data lines 121, and thin film transistors 14 are formed on the substrate 10.

  In the present embodiment, the liquid crystal panel 30 has the alignment of the liquid crystal molecules in the liquid crystal layer 40 so that the direction of the slow axis is 45 degrees with respect to the vibration direction of the S-polarized light, that is, the X-axis direction. Yes. That is, as shown in FIG. 3C, the alignment film A is subjected to the alignment treatment on the substrate 10 so that the angle formed by the slow axis and the X axis is 45 degrees. In addition, the alignment film A is subjected to an alignment treatment so that the liquid crystal molecules have a pretilt angle of 5 degrees with respect to the Z-axis direction so that the liquid crystal molecules driven when a voltage is applied are inclined in the slow axis direction. ing. Although description is omitted, the alignment treatment of the alignment film B is similarly performed on the substrate 20.

  In the liquid crystal device 100 configured as described above, when a voltage is applied to the liquid crystal layer 40 for each pixel, the brightness of an image displayed by the liquid crystal device 100 according to the applied voltage, that is, the polarization beam splitter 5. The amount of light emitted from the viewer to the viewer side changes. The relationship between the voltage and brightness obtained in this example is shown in FIG. In the figure, the horizontal axis indicates the voltage (V) applied to the liquid crystal layer. The vertical axis indicates the brightness of the image displayed by the pixel when the voltage (V) is applied, as a value normalized with the maximum brightness being “1”. Note that the brightness of the image shown in FIG. 4A is the brightness of the pixel in the Z-axis direction.

  As shown in the figure, in the liquid crystal device 100 of the present embodiment, the brightness is maximum when the voltage is “3.1 V”. And in the voltage before and behind that, the voltage which exhibits the same brightness exists. For example, the voltages with brightness of about 0.95 are “2.8V” and “3.4V”. Alternatively, the voltages with brightness of about 0.82 are “2.6V” and “3.9V”.

  By the way, in this embodiment, since the liquid crystal panel 30 is driven by the VA system for the liquid crystal molecules, the tilt of the liquid crystal molecules may be considered to correlate with the voltage applied to the liquid crystal layer 40. In addition, the amount of inclination of the liquid crystal molecules from the Z-axis direction may be larger at the center of the liquid crystal layer 40 and smaller in the vicinity of the alignment film A and alignment film B. As an example, FIG. 4B shows the inclination of the liquid crystal molecules in the liquid crystal layer 40 with respect to the voltage “2.8 V” and the voltage “3.4 V” exhibiting the same image brightness as described above. In the figure, the horizontal axis indicates a tilt angle (also referred to as “polar angle”) that is an inclination angle with respect to the Z-axis direction. The vertical axis indicates the thickness of the liquid crystal layer 40 normalized by setting the total thickness of the liquid crystal layer 40 (that is, the distance from the alignment film A to the alignment film B) as “1”.

  As shown in the figure, in the liquid crystal device 100 of the present embodiment, the tilt of the liquid crystal molecules is maximum near the center of the liquid crystal layer 40 when the voltage is “2.8 V”, and the tilt angle is approximately 63 degrees. On the other hand, when the voltage is “3.4 V”, the inclination of the liquid crystal molecules becomes maximum near the center of the liquid crystal layer 40, and the tilt angle is about 75 degrees. As an example, out of the layer thickness of the liquid crystal layer 40, the liquid crystal molecules are 60 at a voltage of “3.4 V” than the range P in which the liquid crystal molecules exhibit a tilt angle of 60 degrees or more at a voltage of “2.8 V”. The range Q exhibiting a tilt angle of more than 1 degree is clearly wider.

  As described above, the degree of inclination of the liquid crystal molecules in the liquid crystal layer 40 with respect to the Z-axis direction varies depending on the voltage. Is added, it is assumed that the brightness on the XY plane when viewed from the direction inclined with respect to the Z axis, that is, the viewing angle characteristics are different.

  Therefore, the viewing angle characteristics in the liquid crystal device 100 are examined in two directions, ie, the orientation direction of the liquid crystal molecules, that is, the slow axis direction, and the direction orthogonal to the liquid crystal molecule, where it is estimated that a significant change in optical characteristics appears. FIG. 5 is an explanatory diagram showing directions defined when examining viewing angle characteristics. As shown in the figure, the azimuth angle is 0 ° -180 ° for the X-axis direction, the azimuth angle is 45 ° -225 ° for the slow axis direction of the liquid crystal panel 30, the azimuth angle is 90 ° -270 ° for the Y-axis direction, A direction orthogonal to the slow axis is represented as an azimuth angle of 135 degrees to 315 degrees. Further, the Z-axis direction is set to a polar angle of 0 degree, and in the azimuth angle of 45 degrees to 225 degrees, the inclination direction toward the azimuth angle of 45 degrees is a positive direction, and the inclination toward the azimuth angle of 225 degrees is a negative direction. Similarly, in the azimuth angle of 135 degrees to 315 degrees, the inclination direction toward the azimuth angle of 135 degrees is a positive direction, and the inclination toward the azimuth angle of 315 degrees is a negative direction.

  Now, with respect to the voltage “2.8V” and the voltage “3.4V” exhibiting the same brightness (the same brightness in the Z-axis direction), as an example, the G pixel (in this embodiment, the wavelength of transmitted light is 550 nm). The results of examining the phase difference in two directions are shown in FIG. As shown in the figure, when the polar angle is in the range of −40 degrees to +40 degrees, with respect to the voltage “2.8 V”, the azimuth angle 135 degrees to 315 degrees has a larger phase difference, and conversely, the voltage “3.4 V”. ", The azimuth angle of 45 degrees to 225 degrees has a larger phase difference. Here, although detailed explanation is omitted, it is shown that the image becomes brighter as the value of the phase difference approaches ½ of the wavelength of light incident on the liquid crystal device 100 (here, 275 nm). Therefore, the value of the phase difference shown in FIG. 6 is a value in the range of ½ or less of the wavelength, which means that the larger the value of the phase difference is, the brighter it is.

  From the result of FIG. 6, the viewing angle characteristic of the voltage “2.8V” has a bright direction in the direction of the azimuth angle 135 degrees to 315 degrees, and conversely, the voltage “3.4 V” Since the direction of the azimuth angle 45 degrees to 225 degrees is bright, this direction has a clear vision direction. In other words, the liquid crystal device 100 according to the present embodiment has a characteristic that the clear viewing direction changes depending on the voltage applied to the pixel. Although explanation is omitted, the same applies to other R pixels and B pixels.

  In the present embodiment, using this characteristic, each pixel of the liquid crystal panel 30 constituting the liquid crystal device 100 included in the electronic viewfinder 1 is applied to the pixel within a unit display period of an image to be displayed, that is, within one frame period. The viewing angle of the displayed image is widened by changing the voltage. The observer of the electronic viewfinder 1 may actually see the image from a direction inclined with respect to the Z axis. Therefore, by widening the viewing angle of the image (color image) displayed by the liquid crystal device 100, it is possible to display an image with uniform brightness even when viewed by an observer from an oblique direction.

  This will be described with reference to FIG. FIG. 7 is an explanatory diagram showing how the viewing angle characteristic is compensated in one pixel. FIG. 7A shows the pixel electrode when the voltage output from the data line 121 is applied to the pixel electrode. FIG. 7B is a schematic diagram showing contours of image brightness for all azimuth angles and viewing angles with an absolute value of the polar angle within 40 degrees. FIG.

  As shown in FIG. 7A, the output signal of the data line 121 for compensating the viewing angle characteristic for the compensation pixel to be compensated for the viewing angle is, for each frame period F serving as the unit display time of the image. Are repeatedly output to change the voltage of the pixel electrode. That is, in one frame period F from time t1 to time t11, in this embodiment, when the thin film transistor 14 corresponding to the compensation pixel is turned on by the signal of the scanning line 111, the first half period F / of the one frame period F The voltage of the pixel electrode is “2.8V” from the time t1 to the time t2 that becomes 2 and the voltage of the pixel electrode is “3.4V from the time t2 that becomes the second half period F / 2 of the one frame period F to the time t11. "

  Specifically, a signal for turning on the thin film transistor 14 is output to the scanning line 111 to which the compensation pixel is connected every half of one frame period F. Each time the thin film transistor 14 is turned on, the voltage “2.8 V” and the voltage “3.4 V” output to the data line 121 are alternately applied to the pixel electrode.

  Note that, during the period in which the voltage “2.8 V” and the voltage “3.4 V” output to the data line 121 are applied to the pixel electrode, the thin film transistor 14 is actually turned on by the signal of the scanning line 111. Each pixel is provided with a storage capacitor (not shown), and the voltage applied to the pixel electrode is approximately the voltage value until the next voltage is applied to the pixel electrode. Is retained.

  When the voltage of the pixel electrode changes in this way, the viewing angle characteristics of the image displayed in the compensation pixel are the viewing angle characteristics of the voltage “2.8 V” in the first half of one frame period F and the one frame period F. The viewing angle characteristic obtained by combining the viewing angle characteristic of the voltage “3.4 V” in the latter half of the first half, that is, the viewing angle characteristic integrated in terms of time.

  Specifically, as shown in FIG. 7B, the brightness at each viewing angle is synthesized, and the viewing angle characteristics are compensated. More specifically, the pixel when the voltage of the pixel electrode is “2.8 V” is in a state of displaying an image that exhibits contour lines of brightness as illustrated. That is, the direction of a bright image with a normalized brightness of “0.88” or more is an azimuth angle of 135 degrees to 315 degrees, and the direction of an azimuth angle of 45 degrees to 225 degrees orthogonal to the azimuth angle direction is It has a viewing angle characteristic that becomes gradually darker as it is tilted from the Z-axis. On the other hand, the pixel when the voltage of the pixel electrode is “3.4 V” is in a state of displaying an image that exhibits a contour line of brightness as illustrated. That is, the direction of a bright image with a normalized brightness of “0.88” or more is an azimuth angle of 45 degrees to 225 degrees, and the direction of an azimuth angle of 135 degrees to 315 degrees orthogonal to the azimuth angle direction is It has a viewing angle characteristic that becomes gradually darker as it is tilted from the Z-axis. Therefore, the display state of the pixel when the voltage “2.8 V” is applied and the display state of the pixel when the voltage “3.4 V” is applied have viewing angle characteristics that are complementary to each other. is there.

  As a result, when the two display states are each temporally integrated by 1/2 of one frame period F, the pixel exhibits a display state as shown in the lower side of the drawing in one frame period F. That is, the brightness in the direction of azimuth 45 degrees to 225 degrees with respect to the voltage “2.8 V” is compensated by the brightness in the direction of azimuth angles 45 degrees to 225 degrees with respect to the voltage “3.4 V”. It spreads in the azimuth direction. Thus, according to the present embodiment, the viewing angle characteristics are improved by temporally integrating and synthesizing two display states having the same image brightness and complementary viewing angle characteristics. Thus, a display with a wide viewing angle can be easily obtained without changing the brightness of the image.

  In this embodiment, the two display states are each formed in half of one frame period F. This is because, if two display states having complementary viewing angle characteristics are formed in the same time period within the image display period, the probability that an image synthesized by temporal integration will be an image with a wide viewing angle. Because it becomes higher. Of course, the two display states may be formed with different time lengths in one frame period F. Needless to say, based on the viewing angle characteristics of the two display states to be combined, the respective display time ratios may be changed so that the viewing angle characteristics when they are temporally integrated and combined become wider.

  By the way, in this embodiment, the viewing angle characteristics of the voltage “3.1 V” at which the brightness of the pixel is the brightest were examined. The result is shown in FIG. As shown in the figure, in this embodiment, it can be seen that the viewing angle at the voltage “3.1 V” exhibits approximately the same brightness in all azimuth directions. Therefore, based on the above-described viewing angle at the voltage “2.8 V” and the voltage “3.4 V”, in this embodiment, a voltage higher and lower than the voltage at which the brightness is brightest for the compensation pixel. It can be seen that the clear vision direction in the display state of the pixels is complementary. As a result, according to the present embodiment, two voltages that provide the same image brightness and a viewing angle that is complementary to each other are divided in one frame period (in this embodiment, divided into halves). ), It is possible to obtain a color image with a wide viewing angle.

  The embodiments of the present invention have been described with reference to the examples. However, the present invention is not limited to these examples, and can be implemented in various forms without departing from the spirit of the present invention. Of course. Hereinafter, a modification will be described.

(First modification)
In the above embodiment, as a method for compensating the viewing angle characteristics in each pixel, as shown in FIG. 7, two different voltages are applied to the liquid crystal layer 40 at different times in one frame period F, and the viewing angle characteristics are improved. Of course, the temporal integration is used for compensation, but the present invention is not limited to this. For example, one pixel is divided into two or more sub-pixels, and voltages having a complementary viewing angle characteristic are applied to the liquid crystal layer 40 in one frame period F for each of the divided sub-pixels. Thus, the viewing angle characteristics may be spatially integrated and compensated.

  This modification will be described with reference to FIGS. FIG. 9 is an explanatory diagram showing a configuration of the substrate 10 constituting the liquid crystal panel 30 in which one pixel is divided into two sub-pixels as an example of this modification. FIG. 10 is an explanatory diagram showing how the viewing angle characteristic is compensated in one pixel. FIG. 10A shows the pixel electrode when the voltage output from the data line 121 is applied to the pixel electrode. FIG. 10B is a schematic diagram showing contours of the brightness of the image for all azimuth angles and viewing angles with an absolute value of the polar angle within 40 degrees. is there. In FIG. 9, the same components as those of the substrate 10 (see FIG. 2) in the above embodiment are denoted by the same reference numerals. FIG. 10B is the same as FIG. 7B in the above embodiment. Accordingly, the description thereof is omitted here.

  First, the substrate 10 will be described with reference to FIG. The substrate 10 of this modification is configured by dividing one pixel (R pixel, G pixel, and B pixel) into two sub-pixels adjacent in the X-axis direction, as surrounded by a thick solid square in the drawing. ing. That is, for example, the two sub-pixels Ra and Rb constituting one R pixel have substantially the same shape so as to have substantially the same area area of the pixel in this modification, and the voltage signal supplied from the data line 121a In order to apply a voltage signal supplied from the data line 121b to each pixel, a thin film transistor 14a and a thin film transistor 14b are individually formed. Then, the same image (brightness) is displayed on the two subpixels Ra and Rb, and the voltage signal output from the data driving circuit 12 is controlled so as to function as one R pixel.

  In addition, in this modified example, in order to make the explanation easy to understand, FIG. 9 shows a state in which a total of nine pixels are formed in the X-axis direction and the Y-axis direction, respectively. Similar to the example, about several hundred to several thousand color pixels in the X-axis direction and Y-axis direction (two times as many sub-pixels in the X-axis direction) are normally formed.

  Next, a viewing angle compensation method will be described. In this modification, with respect to the compensation pixel to be compensated for the viewing angle, the pixel voltage applied to the liquid crystal layer 40 is applied to the data line 121a and the data line 121b corresponding to the sub-pixels constituting the compensation pixel as shown in FIG. A predetermined voltage is repeatedly output every one frame period F which is a unit display time of an image so as to exhibit the voltage shown in FIG. That is, in one frame period F from time t1 to time t11, when the thin film transistor 14a and the thin film transistor 14b are turned on by the signal of the scanning line 111 for two subpixels corresponding to the compensation pixel, the one frame period F is obtained. From time t1 to time t11 (from time t11 to time t21), the voltages exhibited by the pixel electrodes in the two sub-pixels are two different voltages for displaying images of the same brightness. In this modification, as an example, the voltage “2 Each of the voltages “2.8V” and 3.4V is repeatedly output so that the voltage becomes “.8V” and the voltage “3.4V”.

  As described above, when the pixel electrodes of the two sub-pixels simultaneously exhibit different voltages “2.8 V” and “3.4 V”, the viewing angle characteristic of the image displayed on the compensation pixel is the voltage “2.8 V”. ”And a viewing angle characteristic with a voltage of“ 3.4 V ”, that is, a viewing angle characteristic that is spatially integrated.

  Specifically, as shown in FIG. 10B, in each sub-pixel, each of the viewing angles formed in accordance with the voltage “2.8V” and the voltage “3.4V” exhibited by the pixel electrode. The brightness is synthesized and the viewing angle characteristics are compensated as shown in the lower side of the figure. The specific composition shown in FIG. 10B is the same as that in the above-described embodiment (see FIG. 7B), and the description thereof is omitted here.

  As described above, in this modification, for example, the voltage “2.8 V” and the voltage “3.4 V” are formed so that display states having viewing angle characteristics that are complementary to each other are formed simultaneously in two adjacent sub-pixels. Are applied to the pixel electrodes of the respective sub-pixels. As a result, since the viewing angle characteristics are improved by spatially integrating the two display states, a display having a wide viewing angle can be easily obtained without changing the brightness of the image as in the above embodiment. It is possible.

  In the present modification, the area areas of two adjacent sub-pixels are set to substantially the same size (shape). This means that if images having complementary viewing angle characteristics are simultaneously displayed in the same region area during the image display period, the spatially integrated and synthesized image has a probability of becoming an image with a wide viewing angle. Because it becomes high. Of course, the sub-pixels may be divided and configured to have different area areas. Based on the viewing angle characteristics of the two display states to be combined, it is only necessary to change the area (or shape) of each region so that the viewing angle characteristics when spatially integrated and combined are widened. Needless to say.

(Second modification)
In the above-described embodiments and modifications, the liquid crystal device 100 exhibits the same brightness and compensates for the viewing angle characteristics using two voltages, a voltage higher than a voltage at which the brightness is maximum and a voltage lower than the voltage at which the brightness is maximized. Although the corner is obtained, it is needless to say that the voltage is not necessarily limited to two voltages exhibiting the same brightness.

  As shown in FIG. 4A in the above embodiment, there is a range of voltages that exhibit the same brightness at voltages higher and lower than the voltage at which the brightness is maximized. For this reason, the range of the brightness of an image that can widen the viewing angle characteristics using a voltage that can obtain the same brightness is limited. Incidentally, in FIG. 4A, the brightness of the standardized image is limited to approximately 0.68 or more (at this time, the applied voltage is a voltage range of approximately 2.5 V or more (5 V or less)).

  Therefore, as described in the above-described embodiment, the two voltages, which are higher and lower than the voltage at which the brightness is maximized, have different viewing angle characteristics. If the viewing angle characteristic is compensated by using the complementary relationship of the viewing angle characteristics existing in the image, it is possible to obtain an image having a wide viewing angle characteristic even in the brightness where two voltages having the same brightness do not exist. .

  As an example, a case where the viewing angle characteristics are compensated by using a voltage “2.2 V” and a voltage “3.8 V” as two voltages will be described with reference to FIG. 11. As is clear from FIG. 4A, these voltages are voltages that are higher and lower than the voltage “3.1 V” at which the brightness is maximized, and have different brightness.

  FIG. 11 is an explanatory diagram showing how the viewing angle characteristic is compensated for in one pixel. FIG. 11A shows how the voltage of the pixel electrode is changed by the voltage output from the data line 121. FIG. 11B is a diagram showing the brightness of the image with contour lines for all azimuth angles and viewing angles where the absolute value of the polar angle is within 40 degrees.

  In this modification, with respect to the compensation pixel to be compensated for the viewing angle, the voltage of the pixel electrode is set to one frame period corresponding to the unit display time of the image as shown in FIG. It is configured to repeatedly present a predetermined voltage every F. That is, in the one frame period F from the time t1 to the time t11, when the thin film transistor 14 corresponding to the compensation pixel is turned on by the signal of the scanning line 111, the time t1 becomes a period of two thirds before the one frame period F. The voltage is “2.2 V” from time t3 to time t3, and is set to voltage “3.8 V” from time t3 that is the remaining one third period of one frame period F to time t11.

  As the pixel electrodes exhibit different voltages in this way, when the respective voltages are applied to the liquid crystal layer 40, the viewing angle characteristics of the image displayed in the compensation pixel are two-thirds before the one-frame period F. The viewing angle characteristic when the voltage is “2.2V” is compensated by the viewing angle characteristic when the voltage is “3.8V” in the remaining third of one frame period F, that is, the time ratio. The viewing angle characteristics are integrated accordingly.

  Specifically, as shown in FIG. 11B, the brightness at each viewing angle is integrated and synthesized according to the time ratio, and the viewing angle characteristics are compensated. More specifically, when the voltage “2.2 V” is applied, the pixel is in a state of displaying an image having a contour line with brightness as illustrated. That is, the direction of a bright image having a normalized brightness of “0.40” or more is an azimuth angle of 135 degrees to 315 degrees, and has a viewing angle characteristic that gradually becomes darker in both directions orthogonal to the azimuth angle direction. On the other hand, when the voltage “3.8 V” is applied, the pixel is in a state of displaying an image having a contour line with brightness as illustrated. That is, the direction of a bright image having a normalized brightness of “0.79” or more is an azimuth angle of 45 degrees to 225 degrees, and has a viewing angle characteristic that becomes gradually darker in both directions orthogonal to the azimuth angle direction. Therefore, the display state of the pixel when the voltage “3.8 V” is applied has a viewing angle characteristic that is complementary to the display state of the pixel when the voltage “2.2 V” is applied. ing.

  When the two display states are temporally integrated, the pixel exhibits a display state as shown in the lower side of the drawing in one frame period F. That is, the brightness in the direction of the azimuth angle 45 degrees to 225 degrees with respect to the voltage “2.2 V” is compensated by the brightness in the direction of the azimuth angle 45 degrees to 225 degrees with respect to the voltage “3.8 V”. It can be seen that the brightness is uniform in the azimuth direction. In this way, according to this modification, the viewing angle characteristics are improved, and a display with a wide viewing angle can be obtained.

  In this modification, as shown in FIG. 11B, with respect to the brightness (0.4 to 0.41) in the Z-axis direction (that is, the center) when the voltage is “2.2 V”, The brightness (0.79 to 0.86) in the Z-axis direction (that is, the center) when the voltage is “3.8 V” is considerably brighter. Therefore, when using a combination of voltages exhibiting different brightnesses as in this modification, the brightness in the Z-axis direction is originally displayed in the compensation pixel in the viewing angle characteristics in a temporally integrated state. It is preferable to adjust the division time of one frame period so that the brightness of the image to be obtained is obtained.

(Third Modification)
In the above embodiment, the liquid crystal device 100 is configured by the liquid crystal panel 30 and the phase difference plate 50. However, the configuration is not limited to this, and the phase difference plate 50 may not be provided. When the phase difference plate 50 is not provided, since optical compensation is not performed, it is assumed that the viewing angle characteristics of the pixel are different from those when the phase difference plate 50 is provided.

  Accordingly, the viewing angle characteristics of the two voltages (voltage “2.8V” and voltage “3.4V”) used in the above embodiment will be described with reference to FIG. FIG. 12 is similar to FIG. 6 in the above-described embodiment, with respect to the voltage “2.8 V” and the voltage “3.4 V”, the azimuth angle is 45 degrees to 225 degrees and the azimuth angle is 135 degrees to 315 degrees in two directions. The result of examining the phase difference is shown. As shown in the figure, when the phase difference plate 50 is not provided, the polar angle is in the range of −40 degrees to +40 degrees, and the voltage “2.8 V” has a larger phase difference at the azimuth angle of 45 degrees to 225 degrees. On the contrary, for the voltage “3.4 V”, the azimuth angle of 135 degrees to 315 degrees has a larger phase difference. That is, this is the reverse of the case where the phase difference plate 50 is provided.

  In the present modification, the viewing angle characteristics shown in FIG. 12 show that the viewing angle characteristics of the voltage “2.8V” are bright in the direction of the azimuth angle of 45 degrees to 225 degrees, unlike the above embodiment. The direction has a clear vision direction, and conversely, for the voltage “3.4 V”, the direction of the azimuth angle 135 degrees to 315 degrees is bright and thus has a clear vision direction. In other words, the liquid crystal device 100 of the present modification has a characteristic that the clear vision direction changes depending on the voltage applied to the pixels even when the phase difference plate 50 is not provided. In particular, it can be said that the range of the polar angle from 0 degree to +40 degrees is remarkable.

  In the liquid crystal device 100 (ie, the liquid crystal panel 30) according to the present modification, an example in which viewing angle characteristics are compensated by using two voltages that are the same brightness and that are higher and lower than the voltage that maximizes brightness. Will be described with reference to FIG.

  FIG. 13 is an explanatory diagram showing how viewing angle characteristics are compensated for in one pixel for two voltages “2.6 V” and “3.9 V” that exhibit the same brightness. FIG. 13A is a diagram showing the brightness of the pixels with contour lines for all azimuth angles and viewing angles in which the absolute value of the polar angle is within 40 degrees. FIG. 13B is a diagram for explaining one method of using the liquid crystal device 100 having the viewing angle characteristics compensated in the present modification. In the present modification, the viewing angle characteristics may be integrated temporally or spatially for the compensation pixels that are to be compensated for the viewing angle.

  In this modified example, as shown in FIG. 13A, the brightness at each viewing angle is synthesized at the same ratio, and the viewing angle characteristics are compensated. More specifically, when the voltage “2.6 V” of the pixel electrode is applied to the liquid crystal layer 40, the pixel is in a state of displaying an image exhibiting a contour line of brightness as illustrated. That is, the direction of a bright image with a normalized brightness of “0.77” or more is an azimuth angle of 45 degrees to 225 degrees, and the direction orthogonal to the azimuth angle direction is gradually particularly in the direction of an azimuth angle of 135 degrees. It has a viewing angle characteristic that darkens.

  On the other hand, when the voltage “3.9 V” of the pixel electrode is applied to the liquid crystal layer 40, the pixel is in a state of displaying an image having brightness contour lines as illustrated. That is, the direction of a bright image having a normalized brightness of “0.78” or more is a direction with an azimuth angle of 135 degrees, and has a viewing angle characteristic that lightens gradually in a direction orthogonal to the azimuth angle direction. In the azimuth angle direction of 135 degrees, the pixel electrode voltage “3.9 V” is applied to the liquid crystal layer 40 with respect to the display state of the pixel when the pixel electrode voltage “2.6 V” is applied to the liquid crystal layer 40. The display state of the pixel when applied to has a viewing angle characteristic that is complementary.

  In the present modification, when the two display states are integrated over time, the pixel exhibits a display state as shown on the lower side of FIG. That is, the brightness in the direction of the azimuth angle of 135 degrees with respect to the voltage “2.6 V” is compensated by the brightness in the direction of the azimuth angle of 135 degrees with respect to the voltage “3.9 V”, and the brightness is approximately uniformed. I understand. Thus, according to the present modification, the characteristics are improved so that the viewing angle at which the brightness is relatively low is reduced, and as a result, a display with a wide viewing angle can be obtained.

  In this modified example, as shown in FIG. 13A, in the integrated viewing angle characteristics, the brightness in the direction of the azimuth angle 45 degrees to 225 degrees is in the direction in which the absolute value of the polar angle increases. It exhibits a symmetrical characteristic that becomes brighter. In addition, the brightness in the direction of the azimuth angle of 135 degrees to 315 degrees also exhibits a substantially symmetric characteristic although it becomes darker in the direction in which the absolute value of the polar angle increases.

  Therefore, in this modification, as shown in FIG. 13B, the liquid crystal device 100 is rotated so that the direction of the azimuth angle of 45 degrees is directed to the direction of the azimuth angle of 180 degrees in the original X-axis direction. It is preferable. In this way, the left and right (X-axis direction) and vertical (Y-axis direction) viewing angle characteristics can be made approximately symmetrical. In this case, for example, when viewing the image from the left and right direction in particular, the brightness is compensated so that the brightness is symmetric when viewed from the left and right direction with respect to the image. Can be even with respect to the corners. As a result, it is possible to provide an image in which an uncomfortable appearance is suppressed. Of course, when the viewing direction is specified, the direction of the azimuth angle may be rotated and used in accordance with the specified direction.

(Other variations)
In the above embodiment, when the viewing angle characteristic is spatially integrated and compensated, as shown in FIG. 9, the shape of the pixel is a rectangular shape and has approximately the same area, and two adjacent pixels in the X-axis direction. Although described as using sub-pixels, the present invention is not limited to this. For example, two subpixels adjacent in the Y-axis direction instead of the X-axis direction may be used. Furthermore, the pixels may not be adjacent to each other and may be spaced apart.

  In the above embodiment, the liquid crystal device 100 is a reflective display device. However, the present invention is not limited to this and may be a transmissive display device. In the case of the transmissive type, it is predicted that the probability that the viewing angle characteristic is symmetric in the positive direction and the negative direction of the polar angle will be lower than that of the reflective type. If the different viewing angle characteristics appear, it is possible to compensate for the viewing angle characteristics by applying the different voltages divided in time or space as described above.

  In the above embodiment, the liquid crystal device 100 is a device that performs color display using the R, G, and B filter layers. However, the present invention is not limited to this, and may be a device that performs monocolor (for example, black and white) display. In the case of a monochromatic display device, it is not always necessary to form the R, G, and B filter layers on the substrate 20.

  In the above embodiment, the liquid crystal device 100 is described as being provided in the electronic viewfinder 1 as an electronic device. However, the present invention is not necessarily limited to this. For example, the electronic device including the liquid crystal device 100 may be a head mounted display. Alternatively, it may be an image projection device such as a projector, or a video device such as a television. Alternatively, it may be a computer device or a portable device. In addition, when providing in a head mounted display and other apparatuses including the electronic viewfinder 1, the light source with which the liquid crystal device 100 is provided is not limited to an LED, but a light source suitable for electronic apparatuses such as a mercury lamp or a fluorescent tube is used. Is preferred.

1 is a perspective view schematically illustrating a schematic configuration of an electronic apparatus including a liquid crystal device according to an embodiment of the present invention. Explanatory drawing about the board | substrate which comprises a liquid crystal panel. It is explanatory drawing explaining the whole structure of a liquid crystal panel, (a) is a top view, (b) is sectional drawing, (c) is a schematic diagram which shows the mode of orientation of a liquid crystal molecule. 4A and 4B are explanatory diagrams illustrating characteristics of a liquid crystal device, in which FIG. 4A is a diagram illustrating a relationship between voltage and brightness, and FIG. Explanatory drawing which showed the direction defined when examining a viewing angle characteristic. Explanatory drawing which showed the relationship between a voltage and phase difference (brightness). It is a figure explaining the mode of compensation of a viewing angle characteristic, (a) is a timing diagram which shows the mode of the change of the voltage of a pixel electrode, (b) is the schematic diagram which showed the brightness of the image with the contour line. The schematic diagram which showed the brightness of the image with the contour line in the voltage where brightness becomes the maximum. Explanatory drawing which shows the structure about the board | substrate which comprises the liquid crystal panel by which the 1st modification divided | segmented one pixel into two subpixels. It is explanatory drawing which showed the mode of the viewing angle characteristic compensation performed in the 1st modification, (a) is a timing diagram which shows the mode of the voltage of a pixel electrode, (b) showed the brightness of the image with the contour line. Pattern diagram. FIG. 9 is an explanatory diagram showing a state of viewing angle characteristic compensation performed in one pixel in a second modification, (a) is a timing diagram showing a state of change in voltage of a pixel electrode, and (b) is an image of an image. The schematic diagram which showed the brightness with the contour line. Explanatory drawing which showed the relationship between a voltage when not providing a phase difference plate, and phase difference (brightness) about two different voltages in the 3rd modification. Explanatory drawing which showed the mode of compensation of the viewing angle characteristic performed in one pixel in the 3rd modification.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Electronic viewfinder, 3 ... Optical system, 5 ... Polarizing beam splitter, 10 ... Substrate, 11 ... Scanning drive circuit, 12 ... Data drive circuit, 14, 14a, 14b ... Thin film transistor, 20 ... Substrate, 30 ... Liquid crystal panel , 40 ... liquid crystal layer, 50 ... phase difference plate, 100 ... liquid crystal device, 111 ... scanning line, 121, 121a, 121b ... data line.

Claims (11)

A pair of opposing substrates;
A liquid crystal layer sandwiched between the pair of substrates and initially oriented in a substantially normal direction with respect to the pair of substrates;
A pixel for displaying an image;
A liquid crystal device having
A liquid crystal device, wherein a first display state and a second display state in which viewing angle characteristics of an image displayed by the pixels are complementary to each other are combined and displayed. The liquid crystal device according to claim 1,
The liquid crystal device, wherein a voltage value applied to the liquid crystal layer in the first display state is different from a voltage value applied to the liquid crystal layer in the second display state. The liquid crystal device according to claim 2,
The voltage value of the voltage applied to the liquid crystal layer in the first display state is a voltage range higher than the voltage value of the voltage at which the brightness of the image displayed by the pixel is maximized, and the second The voltage value of the voltage applied to the liquid crystal layer in the display state is set to a voltage range lower than the voltage value of the voltage at which the brightness of the image displayed by the pixel is maximized. apparatus. The liquid crystal device according to claim 2, wherein
A liquid crystal device having a period driven in the first display state and a period driven in the second display state within the image display period. The liquid crystal device according to claim 4,
The period driven in the first display state and the period driven in the second display state are periods having the same time length. The liquid crystal device according to claim 2, wherein
The pixel is composed of a plurality of sub-pixels,
The plurality of sub-pixels include the sub-pixel driven in the first display state and the sub-pixel driven in the second display state. . The liquid crystal device according to claim 6,
The liquid crystal device, wherein the sub-pixel driven in the first display state and the sub-pixel driven in the second display state have the same pixel area size. A liquid crystal device according to any one of claims 1 to 7,
A liquid crystal device, wherein light having a wavelength of any one color of R (red), G (green), and B (blue) is emitted from the pixel. A liquid crystal device according to any one of claims 1 to 8,
A liquid crystal device, wherein a retardation plate having a refractive index in a thickness direction smaller than a refractive index in an in-plane direction with respect to the pixel is disposed outside the pair of substrates. A liquid crystal device according to any one of claims 1 to 9,
The liquid crystal device, wherein the pixel is a pixel that reflects light incident on the pixel and displays the image.   An electronic apparatus comprising the liquid crystal device according to claim 1.

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